MATERIALS OF
CONSTRUCTION FOR
NACE APPLICATIONS
In 1975, the National Association of Corrosion
Engineers (NACE) issued a standard that provided
materials recommendations for sour services (i.e.
applications containing hydrogen sulfide). This
standard, referred to as “NACE MR0175”, listed
acceptable materials, heat treatments and hardness
limits for sour services. The standard was primarily
developed for sour oilfield applications, but was also
adopted by the oil refining industry. One major
distinction between oilfield and refinery applications
not addressed by NACE prior to 2003 is that oilfield
applications tend to contain salt water or brine. The
resulting high level of chlorides in these oilfield
applications creates additional corrosion problems
particularly for stainless steels.
These include: Hydrogen Sulfide concentration, total
system pressure, application temperature, existence of
elemental sulfur, and chloride content. The use of this
standard is detailed under NACE MR0175-2003
Applicability later in this bulletin.
DEFINITIONS
Throughout this bulletin the following terms are used:
■
Mol % H2S: The Mol (abbreviation for mole) percentage represents the relative concentration of
H2S in a system by volume. The Mol % is directly
equivalent to ppm by the following relation: 1 Mol
% H2S = 10,000 ppm (by volume) H2S. It is important
to note that Mol % is not the same as mass or weight
percentage. To convert from a mass percentage of
H2S to a mole percentage of H2S, the mass percentage of each constituent must first be divided by its
molecular weight (in grams/mole). The molecular
weight is a physical characteristic of a particular liquid
or gas, and can often be found on the MSDS sheet for
the substance.The resulting value of moles calculated
for each constituent is then converted into a percentage by dividing by the total sum of moles calculated
for all the constituents. Example 1 shows how Mol %
H2S is calculated for one application.
■
Psia: Refers to Absolute Pressure in pounds per
square inch. Equals Gage Pressure (psig) + 14.7.
■
Partial Pressure: Equals the Total System Pressure
(psia) multiplied by the Mol % H2S divided by 100.
Note that the charts are plotted with Total System
Pressure (psia) on the y-axis and Mol % H2S on the
x-axis, with lines of constant partial pressure also
shown. In order to use these charts, the user needs to
know either the partial pressure of the application,
or a combination of the total system pressure (psia)
and the Mol % H2S. In other words, if the total system
pressure (psia) and the Mol % H2S are known, the
user does not need to calculate the partial pressure.
To address this basic difference between the two
applications, NACE essentially split the original
MR0175 into two specifications in 2003. The new
standard NACE MR0103-2003 entitled “Materials
Resistant to Sulfide Stress Cracking in Corrosive
Petroleum Environments” is very similar to NACE
MR0175 prior to 2003. It is used for refinery applications or for other sour services where no brine or salt
water is present. This standard is detailed under NACE
MR0103-2003 Applicability later in this bulletin.
For oilfield applications containing brine or salt water,
the revised NACE MR0175-2003 should be used. This
specification is now titled “Metals for Sulfide Stress
Cracking and Stress Corrosion Cracking Resistance in
Sour Oilfield Environments” and is clearly focused on
oilfield production. In this environment, not only is
hydrogen sulfide stress cracking a concern, but the
presence of brine or salt water introduces the additional
issue of chloride stress corrosion cracking. This revision
is a drastic change from its predecessor. Many of the
materials allowed previously are either no longer
permitted or severely restricted in their use. The end
user must know a variety of environmental factors in
order to select appropriate materials of construction.
T101-4 • 1/2009
METSO
T101-4
NACE MR0103 - 2003
Applicability
This standard applies to sour refinery applications and to
other sour services where no brine or saltwater is present.
The following paragraphs describe how to assist users in
determining whether or not this specification is applicable
for their application.
3. Free water with pH > 7.6 and 20 ppm (by weight)
dissolved hydrogen cyanide (HCN) in the water and
some dissolved H2S present, or
4. Free water and > 0.05 psia partial pressure H2S in the
gas in processes with a gas phase.
The standard is applicable if the application contains:
Guideline #4 is illustrated in the chart below. Referring
to the definition of partial pressure from page 1, recall
that the user does not need to calculate this value if the
total system pressure and the Mol % H2S are known. In
the latter case, the user could use this chart to determine
if the application falls below or above the black 0.05
psia partial pressure line.
1. > 50 ppm by weight (Note: 50 ppmw = .005% weight
concentration) dissolved Hydrogen Sulfide (H2S) in
free water (water in liquid phase), or
2. Free water with pH < 4 and some dissolved H2S
present, or
Total System Pressure (psia)
10000
Range of Applicability, per Guideline #4, for MR0103 - 2003
1000
0.
05
ps
ia
Pa
r
Environmental Guideline #4
MR0103-2003 Applies
tia
lP
re
s
100
su
re
10
Environmental Guideline #4
MR0103-2003 Does Not Apply
1
0.001
0.01
0.1
1
10
100
Mol % H2S
The following example illustrates how to determine if MR0103 is applicable.
Example 1: Determining Applicability of MR0103
If my total system pressure is 1200 psia, the system pH is 6.5
and I have the following constituents in my application
percentages by mass): 10% methane, 75% carbon dioxide,
.0045% H2S, .3% water and balanced nitrogen, how do I
determine if NACE MR0103-2003 applies?
Constituents
Methane
Carbon Dioxide
Hydrogen Sulfide
Water
Nitrogen
Total:
Mass %
(A)
Molecular Weight (g/mole)
(B)
# Moles
(A/B)
Mol %
# Moles/2.8688 * 100
10
16.044
0.6233
21.7262
75
44.01
1.7042
59.4028
0.0045
34.076
0.00013
0.0046
0.3
18.0153
0.0167
0.5805
14.696
28.0134
0.5246
18.2859
2.8688
100
100
The Mol % H2S was found to be .0046%. We know that the
total pressure is 1200 psia. Referring to the chart, this
application is just above the boundary line.To be sure,we can
2
TECHNICAL BULLETIN 1/09
Example 1: Solution
First, the specification would not apply per the first 3
environmental conditions. The H2S concentration is just
below the level listed in environmental condition #1, and
the pH is not an issue per conditions #2 and #3.
Proceeding to the 4th condition, we must use the chart
above. We first need to calculate Mol % H2S:
calculate the partial pressure as .0046/100 * 1200 = .055
psia, which is greater than 0.05 psia. As a result, NACE
MR0103-2003 would apply per guideline #4.
T101-4
M AT E R I A L S O F C O N S T R U C T I O N F O R N A C E A P P L I C AT I O N S
Acceptable Materials of Construction for NACE MR0103-2003
Material
Cast or Wrought
Restrictions
Cast
22 HRC Max
Cast
When API, ANSI, and/or other industry standards approve its use
ASTM A351 CF8M
Cast
22 HRC Max; Solution annealed
ASTM A351 CG8M
Cast
22 HRC Max; Solution annealed
ASTM A351 CF3M
Cast
22 HRC Max; Solution annealed
Cast
22 HRC Max; Solution annealed
Wrought
22 HRC Max; Solution annealed
Carbon Steel
ASTM A216 Gr. WCB
Ductile Iron
ASTM A395
Austentic Stainless Steels
ASTM A351 CN7M
S31600 (316)**
S31700 (317)**
Wrought
22 HRC Max; Solution annealed
S31603 (316L)**
Wrought
22 HRC Max; Solution annealed
N08020 (Alloy 20)**
Wrought
22 HRC Max; Solution annealed
S20910 (Nitronic 50)
Wrought
35 HRC Max; Solution annealed; Hot-rolled or cold-worked condition
Highly Alloyed Austentic Stainless Steels
ASTM A351 CK-3MCuN
S31254
Cast
35 HRC Max; Solution annealed
Wrought
35 HRC Max; Solution annealed
Wrought
33 HRC Max; H1150M condition
Precipitation Hardenable Stainless Steels
S17400
Nickel Alloys
ASTM A494 M35-1
Cast
35 HRC Max
N10276
Wrought
35 HRC Max; Solution annealed
N05500
Wrought
35 HRC Max; Hot-worked and age-hardened, or solution annealed,
or solution annealed and age-hardened
N07718
Wrought
35 HRC Max; Solution annealed or hot-worked or hot-worked and aged
N07718
Wrought
40 HRC Max; Solution annealed and aged
** Free of cold work that enhances mechanical properties
TECHNICAL BULLETIN 1/09
3
METSO
T101-4
NACE MR0175 - 2003
Applicability
This standard applies to sour oilfield applications
containing brine or salt water.The following paragraphs
describe how to assist users in determining whether or
not this specification is applicable for their application.
This is shown in the chart below. Again, the user does not
need to calculate partial pressure if the total system pressure
and the Mol % H2S are known. In the latter case, the user
could use this chart to determine if the application falls
below or above the black 0.05 psia partial pressure line.
As with MR0103, MR0175-2003 always applies for
applications containing water as a liquid with H2S partial
pressures equal to or greater than 0.05 psia.
MR0175-2003 also has some situations where it does not
apply. These specific cases are:
Range of Applicability for MR0175 specification
10000
Gas Systems, if:
Total System Pressure < 65 psia
(Below the grey line on chart)
1000
05
Gas and Oil Systems
ps
ia
s
re
lP
tia
265 psia Total Pressure
su
re
100
MR0175
Does Not
Apply
e
ia ur
ps ess
10 l Pr
a
rti
Pa
r
Pa
Refer to example 1 on page 2 for an
example showing how to determine the
Mol % H2S and the partial pressure of a
system.
0.
Gas and Oil Systems, if:
Total System Pressure < 265 psia,
and Partial Pressure < 10 psia,
and Mol % H2S < 15
(Below and inside the blue line on chart)
Total System Pressure (psia)
MR0175
Applies
65 psia Total Pressure
Gas Systems
10
0.001
0.01
0.1
1
15%
10
100
Mol % H2S
Determining Materials of Construction
After confirming that NACE MR0175-2003 is applicable for
a given application, the following information is required
in order to select materials of construction:
H2S Mol %
Or Partial Pressure
Total system pressure
(as discussed above)
Application temperature
Existence of elemental sulfur
Chloride content
}
Application Zones for Butterfly and Ball Valve Usage
1500
sia
l
rtia
Pa
ial
art
aP
900
ss
Pre
ure
600
e
sur
res
lP
rtia
Pa
sia
0p
re
10
ssu
Pre
p
50
1200
psi
It is important to note that for some
MR0175-2003 acceptable materials, the
hardness and heat treatment requirements
may be different from the same materials
listed in MR0103-2003. Review the material
requirements listed in this section carefully.
The material options are denoted Tier 1, Tier 2 and Tier 3.
Note that the Tier 1 combination is the least expensive
option, Tier 2 is moderately priced, and Tier 3 is the most
expensive.The user should select the appropriate materials
of construction for an application.
15
Examples 2 and 3 illustrate how these
graphs and tables are used to select the
appropriate materials of construction for
an application.
Total System Pressure (psia)
•
•
•
•
•
Use the chart below to determine the appropriate zone for
the application based on the total system pressure and the
Mol % H2S. Once the appropriate zone is determined,
select the material combination from Tables 1 and 2 for
Butterfly Valves and Tables 3 and 4 for Ball Valves.
ZONE 4
ZONE 3
ZONE 2
ZONE 1
(Any point below
15 psia PP line)
300
0
1
4
TECHNICAL BULLETIN 1/09
10
Mol % H2S
100
T101-4
M AT E R I A L S O F C O N S T R U C T I O N F O R N A C E A P P L I C AT I O N S
Table 1: Butterfly Valve Tier Selection for Zones 1 – 4
Zone 1
Zone 2
Zone 3
& Zone 4
from Application Zones for Butterfly and Ball Valves chart on page 4 (Refer to Table 2 for Tier Definitions)
Tier 1
Max
Elemental
Max Cl
Tier 2
Tier 3
Temp
Sulfur
Content
Not
No
No Elemental Sulfur
No
140˚F
Allowed
Limit
No Other Restrictions
Restrictions
No
No
No Elemental Sulfur
No
50 mg/L
Limit
Limit
No Other Restrictions
Restrictions
Not
No Elemental Sulfur
No
Permitted
No Other Restrictions
Restrictions
Table 2: Tier Definitions for Butterfly Valves
Tier 1
ASTM A216 WCB
22 HRC Max
ASTM A351 CF8M
Solution Annealed
22 HRC Max
S20910 (Nitronic 50)
Solution Annealed and Cold
Worked; 35 HRC Max
Body*
Disc
Shaft
Tier 2
ASTM A216 WCB
22 HRC Max
ASTM A351 CK-3MCuN
Solution Annealed
100 HRB Max
S20910 (Nitronic 50)
Solution Annealed and Cold
Worked; 35 HRC Max
Tier 3
ASTM A216 WCB
22 HRC Max
ASTM A494 CW-12MW
Solution Annealed
52% (Ni + Co) Min
S20910 (Nitronic 50)
Solution Annealed and Cold
Worked; 35 HRC Max
* Disc material may be substituted for body material.
Table 3: Ball Valve Tier Selection for Zones 1 – 4
Zone 1
Zone2
Zone 3
Zone 4
from Application Zones for Butterfly and Ball Valves chart on page 4 (Refer to Table 4 for Tier Definitions)
Tier 1
Tier 2
Max
Elemental
Max Cl
Max
Elemental
Max Cl
Tier 3
Temp
Sulfur
Content
Temp
Sulfur
Content
Not
No
Not
No
140˚F
340˚F
5000 mg/L
Allowed
Limit
Allowed
Restrictions
No
No
Per Chart
Not
No
50 mg/L
5000 mg/L
Limit
Limit
Below
Allowed
Restrictions
Not
Per Chart
Not
No
5000 mg/L
Permitted
Below
Allowed
Restrictions
Not
Not
No
Permitted
Permitted
Restrictions
Table 4: Tier Definitions for Ball Valves
Body*
Ball
Tier 1
ASTM A216 WCB
22 HRC Max
ASTM A351 CF8M or ASTM A479 S31600**
Solution Annealed
22 HRC Max
Tier 2
ASTM A216 WCB
22 HRC Max
ASTM A351 CK-3MCuN Solution Annealed
100 HRB Max or
ASTM A479 S31254 Solution Annealed
Tier 3
ASTM A216 WCB
22 HRC Max
ASTM A494 CW-12MW or
ASTM B574 N10276
Solution Annealed 52% (Ni + Co) Min
ASTM A479 S31600**
Solution Annealed
22 HRC Max
S20910 (Nitronic 50)
Solution Annealed and Cold
Worked; 35 HRC Max
S20910 (Nitronic 50)
Solution Annealed and Cold
Worked; 35 HRC Max
Stem
* Ball material may be substituted for body material.
** Free of cold work that enhances mechanical properties.
Maximum Allowable Temperatures for Tier 2 Materials
Max Temp (˚F) for Tier 2
350
325
300
275
250
ZONE 1
ZONE 2
ZONE 3
225
200
0
20
40
60
Mol % H2S/100 * Total Pressure, psia
80
100
TECHNICAL BULLETIN 1/09
5
Example 2: MR0175 Materials of Construction for
Butterfly Valves
My application contains 2 Mol % H2S @ 1200 psia. What
materials of construction should I use for a butterfly valve if
my application temperature is 300˚F, I have no elemental
sulfur, and my chloride content is 1000 mg/L?
Example 2: Solution
We first refer to the Application Zones for Butterfly and
Ball Valves chart on page 4.We find that the point comprised
by 2 Mol % H2S and 1200 psia appears to fall just above the
green line into Zone 2. To confirm this, we simply calculate
the partial pressure as 2/100 * 1200 = 24 psia, and we do
find that the point falls above the 15 psia partial pressure
boundary line.
We then go to Table 1, where we see that we have 3 material
combination options depending on the application
temperature, the presence of elemental sulfur and the
chloride content.Tier 1 has no requirements on temperature
and elemental sulfur, but the maximum chloride content
allowed is 50 mg/L. Since our chloride content is 1000
mg/L, we cannot use Tier 1.
We next look at Tier 2,where we see that the only requirement
is that there is no elemental sulfur in the system. Since we
comply with this requirement, we can use Tier 2 for this
application. Tier 3 may also be used for this application,
since there are no restrictions on its use, however Tier 2
would be the most cost-effective option.
Example 3: MR0175 Materials of Construction for Ball
Valves
For the application in Example 2, what materials of construction
would I use for a ball valve?
Example 3: Solution
From Example 2, we know that our first step is to refer to
the Application Zones for Butterfly and Ball Valves
chart on page 4, and we know that for this application we
fall into Zone 2.
We then go to Table 3 for ball valves, and look across the
Zone 2 row at the material combinations available. To use
Tier 1, the chloride content must be less than 50 mg/L.
Since our application has 1000 mg/L, we cannot use this
option.
Tier 2 has three requirements,that the maximum temperature
adheres to the Application Zones for Butterfly and Ball
Valves chart on page 4, that there is no elemental sulfur,
and the chloride content is less than 5000 mg/L. For our
application, we have no elemental sulfur and the chloride
content is 1000 mg/L, but we do need to check the
Maximum Allowable Temperatures for Tier 2 Materials
chart on page 5 to determine whether our temperature
complies with the requirements. At 2 Mol % H2S and 1200
psia, the x-axis value in the Application Zones for
Butterfly and Ball Valves chart is computed as 0.02 * 1200
= 24 psia. For this x-axis value, the maximum allowable
temperature for Tier 2 is approximately 325˚F. Since our
temperature is 300˚F, we comply with this requirement
and also comply fully with the requirements for Tier 2.
Tier 3 may also be used since there are no restrictions on
its use, however it is more cost-effective to use the lower
Tier numbers whenever possible.
Subject to change without prior notice.
Metso Automation Inc.
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